A conventional transmission for a powered vehicle includes software or a control scheme for determining when the automatic transmission shifts from one gear range (or ratio) to another gear range. The software or control scheme can include one or more shift schedules for shifting the transmission. The shift schedule can be an economy or performance shift schedule, for example, which controls the shifts based on current driving conditions.
The transmission controller can communicate with an engine in the vehicle. The engine generally includes an engine controller or engine control module. Data or information related to the engine, including torque, power, temperature, pressure, speed, etc., can be communicated to the transmission controller. This data or information can be used by the transmission controller for operating the transmission based on current engine conditions.
In particular, each engine is capable of providing power to the transmission. The engine generally provides different levels of power based on engine speed. The power can be illustrated as a performance curve, for example, in which the power increases to a maximum value. The shape of a performance curve can be different for different engines and this can provide challenges to the transmission controller to adapt the function of the transmission to different engines. This can be particularly challenging to adapt shift schedules for shifting the transmission because the amount of input torque received by the transmission can be different for each engine.
In the past, most engines made peak power at an engine's full load governing speed. However, today's engine manufacturers are being required to reduce emissions and improve fuel economy. To meet these demands, many engines now make peak power at engine speeds less than the full load governing speed. This approach has many consequences to the performance of the transmission. In conventional transmission shift schedules, a transmission would make an upshift (e.g., from a numerically higher gear ratio to a numerically lower gear ratio) near the engine's full load governing speed. As noted, this generally was the point where an engine produced its greatest amount of power. Ideally, the power after making an upshift should be approximately the same as the power before making the shift. This provides the best performance and fuel efficient manner of shifting the transmission.
Due to federal regulations, however, transmission shift schedules must now adapt to different engine performance curves. Since each engine can have its own unique performance curve, transmission shift points can be different for each engine. Thus, shift schedules are dependent on the shape of the engine performance curve and a transmission gear step. Since transmission software must enable a transmission to shift according to any engine performance curve, there is a need for a method to establish shift points for shifting a transmission according to any engine performance curve. There is a further need for determining ideal shift points automatically and in real-time for each gear step based on any engine performance curve.